1. Field of the Invention
Aspects of the present invention relate to a light outputting device integrally provided with a monitoring detector and a light scanning unit having the same, and more particularly, to a light outputting device having a compact configuration and an improved ability to detect a signal used to automatically adjust the amount of light emitted from a vertical cavity surface emitting laser (VCSEL) and a light scanning unit having the same.
2. Description of the Related Art
In general, a vertical cavity surface emitting laser (VCSEL) emits a laser beam in a direction through layers of a wafer, that is, in a vertical direction which is perpendicular to horizontal layer surfaces, unlike an edge emitting laser. Accordingly, since a plurality of VCSELs are capable of being integrated on a signal wafer, a light outputting device using the VCSEL can easily perform scanning operations in two dimensions. Accordingly, the light outputting device using the VCSEL may be widely used for many optical applications, such as laser printing, laser scanning, medical equipment, optical communications, etc.
The light outputting device using the VCSEL should be monitored to automatically control the intensity of a light beam outputted from the VCSEL. Since the VCSEL emits a light beam in one direction unlike the edge emitting laser, the light beam can be used to perform both an intended function of the light beam, such as scanning, and can further be used in a monitoring operation.
In general, to perform the monitoring, a monitoring detector may be provided on an inner part or an outer part of the light outputting device. If the monitoring detector is provided on the outer part of the light outputting device, an additional optical element, such as, a half plate, is necessary to divide the light beam outputted from the VCSEL into two paths. Thus, there is a disadvantage that a manufacturing cost of the light outputting device is increased.
FIG. 1 is a schematic sectional view illustrating a conventional light outputting device having a monitoring detector provided on an inner part of the light outputting device. As shown in FIG. 1, the conventional light outputting device includes a substrate 1, a VCSEL 3 provided on the substrate 1, and a light output control unit 5 to control a light output of the VCSEL 3. The light output control unit 5 includes a monitoring detector 6 provided on the substrate 1 to be adjacent to the VCSEL 3, a housing 7 on which a transparent cover glass 7a is disposed, and an auto power controller (APC) 9. The housing 7 is disposed on the substrate 1 to surround the VCSEL 3 and the monitoring detector 6. The cover glass 7a is positioned on a proceeding path of the light emitted from the VCSEL 3 to transmit most of the light emitted from the VCSEL 3 and reflect a part thereof toward the monitoring detector 6.
In the conventional light outputting device, a part of the light emitted from the VCSEL 3 is reflected by the external surface of the cover glass 7a. The monitoring detector 6 receives the reflected light and transmits the reflected light to the APC 9 after a photoelectric converting operation is performed. Accordingly, the light output of the VCSEL 3 can be controlled.
In the light outputting device having the configuration as shown in FIG. 1, since the amount of the light proceeding toward the monitoring detector 6 is not proportional to the amount of the light emitted from the VCSEL 3 due to various “obstructing factors,” it is difficult to correctly control the light output. Two of the “obstructing factors” are that (1) a divergent angle of the light emitted from the VCSEL 3 varies depending on a driving current and temperature, and (2) there is a diffused reflection. With respect to factor (1), since the amount of the light proceeding toward the monitoring detector 6 among the total amount of the emitted light varies as the divergent angle of the light emitted from the VCSEL 3 varies, it is difficult to detect the amount of the received light in proportion to the amount of the light emitted from the VCSEL 3. With respect to factor (2), a light beam is diffused as it is reflected by the housing 7 and received by the monitoring detector 6, making it difficult to detect the amount of the received light in proportion to the amount of the light emitted from the VCSEL 3.
Also, not all of the light reflected by the cover glass 7a is reflected toward the monitoring detector 6. Accordingly, the amount of current outputted by the monitoring detector 6 decreases, so that the light output of the VCSEL 3 cannot be normally controlled.
According to another example of the conventional light outputting device, a monitoring detector is provided on the inner part of the light outputting device. A substrate of the VCSEL is manufactured to include the monitoring detector within the substrate. That is, by doping an electrode layer of the monitoring detector with the same semiconductor type as a lower reflecting layer of the VCSEL, the substrate of the VCSEL is layered on the monitoring detector. In this case, since the monitoring detector receives the emitted light transmitted through the lower reflecting layer of the VCSEL, the problems associated with the light outputting device shown in FIG. 1 may be reduced.
However, in this light outputting device according to another example, it is necessary to newly manufacture the substrate. In this case, manufacturers may have difficulty in determining a wafer growth condition despite newly manufacturing the substrate.